The present invention is concerned generally with aqueous biphasic extraction processes. More particularly, the invention is concerned with controlling particle size and/or pH levels to control the separation behavior of silica in aqueous biphasic extraction processes.
Aqueous biphasic extraction processes are heterogeneous liquid/liquid systems that result from the use of immiscible combinations of inorganic salts and water-soluble polymers, such as polyethylene glycol. Colloid-size particles that are suspended in an aqueous biphasic system will partition to one of the two immiscible phases, depending on a complex balancing of particle interactions with the surrounding solvent. With regard to waste treatment applications, aqueous biphasic systems are similar to conventional solvent extraction. However, aqueous systems do not utilize an organic diluent which may itself become a source of pollution. While biphasic separation processes are known, there still remain substantial problems in separating particular substances. For example, silica-based substances are considered impurities in numerous common substances, such as clays. Historically, efficient and inexpensive removal of excess silica (which can coexist as a separate phase in a mechanical mixture with silica chemically bonded to desirable materials) from desirable materials, such as kaolin clay in particular, has been unavailable.
It is therefore an object of the invention to provide an improved biphasic aqueous extraction process.
It is a further object of the invention to provide a novel method of separating silica from other materials.
It is another object of the invention to provide an improved aqueous biphasic extraction system for separating silica from other materials.
It is yet a further object of the invention to provide an improved method of separating silica from materials using precise pH control of an aqueous biphasic extraction process.
It is still another object of the invention to provide a novel method of separating silica, metallic oxides and other metallic compounds utilizing control of pH and particle size in combination.
Further objects and advantages of the present invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description of the invention when taken into conjunction with the accompanying drawings.